Method and apparatus for testing materials



May 11 1926. 1,584,320

. J. VV.()VVEP4S METHOD AND APPARATUS FOR TESTING MATERIALS OriginalFiled Feb. 8, 1920 pli ilhll'li hih yarns win JAMES W. OWENS, OFCRADOCK, VIRGINIA, ASEEIGI TOR T0 TIIIIUS O LSEN TESTIKG MACHINECOMPANY, GI? PHILADELEHIA, PENNSYLVANIA, AlCQRFGRAEION 0Fv PENNSYLVANIA.

METHOD AND APPARATUS F031 TESTING MATERIALS.

Original application filed February 3, 192% Serial No. assess. Dividedandthis application filed.

August 19, 1921.

Method for use in connection with the test ing of materials, of whichapplication the present case is a dlvision, I have disclosed method ofobtaining test specimensfrom a completed or finished structure withoutundue impairment or mutilation thereof, and the present invention, whilenot limited in application to test specimens obtained in the abovemanner, is particularly advantageous as used in connection therewith.

This invention also includes the provision of suitable tools andappliances whereby testing operations such as are above mentioned may beefficiently carried out to obtain the desired data on the qualities ofthe material to be tested. I

Further objects and advantages of the invention will bein part obviousand in part specifically pointed out in the description hereinaftercontained, which, taken in connection with the accompanying drawings,discloses a preferred method and apparatus for testing materials inaccordance with the invention; such disclosure, however, is to'beconsidered merely as typical of its principle.

In the drawings:

Figs. 1 and 2 are respectively a frontview and a central section of atest specimen adapted to be tested in accordance with the invention.

Fig. 3 is a central section showing a modilied form of test specimen.

at shows a plug in operative position to test a specimen such as isshown in Figs. 1 to 3.

the test piece.

Serial No. 493,537.

Fig. 5 shows a modification in the manner of applying such a plug to atest specimen.

Figs. 6 and 7 are front and sideviews respectively showing a testspecimen inposition to be tested in a testingmachine, in accordance withthe invention.

Fig. 8 is a section on line 8 8.of' Fig, 6'

looking-in the direction of the arrows. I

Fig. 91s a plan viewof a ductility gage adapted to be used inconnectionwith the testing machine illustrated inFigs. 6 and 7. 10 is asection on line 10 10 of Fig. 9 looking in the direction of the arrows.

In accordance with the present invention, I employ for test specimensannular or'ringshaped pieces suclras the piece 1 of Figs .1

and 2 havinga central hole 2 These specimens may be cut from a metalplate, a. welded joint, or the like, and are finishedaccurately to thedesired thickness and diameter, for instance as described in greaterdetail in my co-pending application. above mentioned, orin any othersuitable manner.

I then subject the test pieces to outwardly servance of its behaviorunderthetaction'of the radial forces abovedescribed.

I prefer to apply stresses of the above character to the test pieces bymeans of a tapered plug 3 as indicated in Fig. 4, the test piece 1 beingseated upon a die 4 having a hole 5 therein alined with the hole 2 ofThus when measured forces are applied to the tapered plug 3 tensilestresses are set up in the test piece throughout its entire crosssection, andthe cross sectional area of the test piece being known,

the tensile strength of the material maybe determined from its behaviorunder test. If

desired, the hole within the test piece 1 may be given a taper 2 asindicated in Fig. 3, to correspond to the taper of plug-3. If this isdone the plug will tend less to crush the walls of the hole as it isforced into the test piece. Or as indicated in Fig. 5, a plurality ofsector-like wedge members 6 having their outer surfaces cylindricallycurved to fit the hole 2 of the test ring and their inner surfaces flatto fit a polygonal tapered plug 3 may be interposed between the specimen1 and the plug, thus avoiding the tendency of the plug to crush theinner walls of the specimen and reducing friction to a large extent withthe result that a greater proportion of the force applied tothe plug istransformed into tensile stresses in the ring of the test piece.

In Figs. 6 and 7 a plug testing device such as is above described isshown as embodied in a testing apparatus adapted to be interposedbetween the opposed heads 7 and 8 of a testing machine. Ihe testingapparatus as a whole is carried upon a base 9 having a recess 10adjacent its top surface within which rests a die st of the characterpreviously described. A plurality of posts 11 extend from the base 9 andslidably support a cross head 12 which carries the tapered plug 3. Inthe present form, the cross head 12 has a hollow hub 13 within which thetapered plug 3 may be inserted with its outer end projecting beyond thehub and seated against the same. A cap 14 having a recess 15corresponding to the shape of head 16 on tapered plug 3 is attached tothe head 7 of the testing machine in such manner that the testingapparatus carried as a whole by base 9. may readily be slid into and outof position between the heads 7 and 8. The apparatus is carefully madeso that the hole within the hub 13 will accurately aline the taperedplug 3 with the hole 5 in die 4, thus placing uniform stresses upon thetest ring 1 when the plug 3 is advanced into it.

The apparatus is arranged to indicate the distance which plug 3penetrates into the test specimens during test, for instance by Yproviding a micrometer dial 17 upon cross head 12, the finger 18 of themicrometer bearing against a stationary inclined straight edge member 19so that the micrometer indicates the amount of vertical movement of thecross head and tapered plug while the test is being carried on. Ihestraight edge member 19'preferably is pivoted to an end plate 20 at theupper end of guide posts 11 and it is angularly adjust able at its lowerend as by means of the set screw 21 extending through a slot 22 in thestraight edge 19 and clamping the straight edge against base 9. If thespeci men to be tested is exceedingly ductile, the

movementvof plug 3 into the specimen may be relatively great so that aslight taper of straight edge 19 may be secured by adjust-ment of screw21; or if the test specimen is very brittle a greater inclination of thestraight edge 19 will be desirable in order to magnify the reading ofthe micrometer dial 17 after a relatively small movement of tapered plug3 into the test specimens. If desired, the downward movcment of thetapered plug 3 may also be registered on a plurality of fixed indicatorbars 23 over which movesa sight 24L carried on cross head 12, Thereadings on each indicator bar show the amount of downward movement of aplug having a certain taper for the corresponding position and crosshead 12.

A counter-weight 25 (Fig. 7) is secured to cross head 12 by means of acord 26 passing over rollers 27 and 28, such counterweight enablinggreater accuracy to be obtained in the readings of force applied to thetest specimen, since it removes the weight of the cross head, taperedplug, etc., from the ring while the latter is under test, and alsoprevents a sudden fall of the cross head at any time.

It has been found that the behavior of the ring specimen when subjectedto the plug test abovedescribed gives a very reli able indication of thetensile strength of the material of which the ring is formed,

the values obtained by the test bearing a substantially constantrelation with those which are obtained when the material is subjected tothe ordinary elongation tests of a testing machine. In fact, thestresses set up by the two tests are quite similar, particularly iffriction between the tapered plug and the hole 2 of the test specimen isreduced as'much as possible. However, the test is much simpler than theelongation test above referred to both in regard to the ease with. whichthe specimens can be obtained and the application of the stresses to thetest piece, which may be done in the plug test by the application ofpressure as distinguished from tension.

I The test may also be employed to determine the ductility of thespecimen either alone or in connection with the determination of thetensile strength thereof. This is accomplished by measuring the increasein periphery of the test specimen when the tapered plug is forced intothe same As shown more in detail in Figs. 9 and 10, the change inperiphery of the specimen may be measured by means of a gage 29 having abody portion 30 adapted to surround the test piece 1 and preferablyhaving means for positioning the test piece centrally within the gage,In the form illustrated, a fixed abutment 31 on the body portioncooperates with a pair of spring pressed plungers 32 adjustable bythumbscrews 33, to bring-thetest specimen intothe test specimen with thefree end of the" band suitably fixed within a slot 35 in alinement withthe slot 35 previously described. The remainingend of band Slis attachedto a measuring device such as a micrometer mounted on a strap 36 whichslides along a graduated arm 37 extending from body portion of the gage.The

band is attached to a reciprocable plunger 38 of the micrometer, theplunger 38 being pressed outwardly by a spring 39 to maintain the band34C taut during the operation of the gage and to insure that any changeof shape of the test specimen will be accurately recorded and indicatedby micrometer pointer 40 moving over the dial 4C1.

As appears particularly in Fig. 10, a plurality of screws 42 or somesimilar device may be used to maintain the body portion 30 of the gagelevel in the testing machine. A bracket 4-3 (Figs. 6 and 7) supports thegraduated arm 37 of the gage, adjusting screws 44. being provided tobring the arm to a horizontal position. Thus, as the test specimenexpands under the stresses applied on tapered plug 3, its changes inperiphery are indicated by pointer 40. The applied stresses, the crosssectional area of the ring, and its increase in periphery due to thestress all being known, the test therefore indi ates the ductility ofthe material under test.

\Vhile certain preferred embodiments of the invention have beendescribed, it will be obvious that many changes may be made thereinwithout departing from .the principle of the invention as defined in thefollowing claims.

I claim:

1. The method of testing the strength of finished structures whichcomprises cutting out a ringshaped test piece of predeterminedcross-sectional area therefrom, inserting a tapering plug into said testpiece and a n il ing measured pressure to said plug to force the sameinto the ring in a direction substantially perpendicular to the plane ofthe ring and set up tensile stresses therein substantially throughoutits cross-sectional area. 7

2. A testing apparatus comprising a base, die carried thereby adapted toreceive a test piece of annular shape, a plurality of posts extendingfrom said base, a cross head slidable along said'posts and a taperingplug carried by said cross" head, said plug being alined'with-sai'd die,said base and cros shead having opposed faces adapted to engagetheopposed heads of thetesting ma; chine.

' 3. A testing apparatus comprising a base, a die carried therebyadapted to receive a test piece of annular shape, a plurality of postsextending from said base, a cross head slidable along said posts havinga hollow hub alined with said die, and a tapering plug within said hubhaving its outer end projecting beyond the hub and seated against thesame, said base and crosshead having opposed faces adapted to engage theopposed headsof the testing machine.

' a. A testing apparatus comprising a base, die carried thereby adaptedto receive a test piece of annularshape, a plurality of posts extendingfrom said base, a cross head slidable along said posts, a tapering plugcarried by said cross head, said plug being alined with said die, andmeans for measuring the travel of said cross head towards said base,said base and crosshead having opposed faces adapted to engage theopposed heads of the testing machine.-

5. l i-testing apparatus comprising a base, a die carried therebyadapted to receive a test piece of annular shape, a plurality of postsextending from said base, a cross head slidable along said posts, atapering plug carried by said cross head, said plug being alined withsaid die, and means for measuring the travel of said orosshead towardssaid base, said means comprising a straight edge member inclined to thepath of travel of the cross head and a micrometer cooperating therewith.

6. A testing apparatus comprising a base, a die carried thereby adaptedto receive a test piece of annular shape, a plurality oi posts extendingfrom said base, a cross head slidable along said posts, a tapering plugcarried by said cross head, said plug being alined with said die, andmeans associated with said apparatus for measuring the inf V crease inperiphery of a test piece when in position on said die. V

7. A testing apparatus comprising a base, a die carried thereby adaptedto receive a test piece of annular shape, a tapering plug alined withsaid die, and a plurality of sector like wedge members adapted to fitwithin an annular test piece, said wedge members having their innersurfaces tapered to fit around said plu V 8. A testing apparatuscomprising a base, a die carried thereby adapted to receive a "est pieceof annular shape, a tapering polygonal plug alined with said die, and aplurality of sector like wedge members adapted to fit within an annulartest piece, said wedge members having flat inner surfaces tapered to fitaround said plug and having outer surfaces of areuete curvature. V

9. A testing apparatus comprising a base, a die carried thereby adaptedto receive a test piece of annular shape, a orosshead c-arrying a,tapering plug, means for guiding said crosshead to slide to and from thebase with the plug alined with the die, said base and orosshesd havingopposed faces adapted to engage the opposed heads of a testing machine.

. In testimony that I claim the foregoing, I have hereunto set my handthis 22 day of July, 1921.

JAMES W. OWENS.

